The present invention relates to a liquid leakage detection system.
Accidents in which crude oil leaks from storage tanks, or other oils and hazardous liquids leak from chemical plants have been increasing and the contamination of the sea, rivers and lakes due to the leakage of various oils and other hazardous liquids have also been on the increase. As a result, pollution control standards and emission control regulations have been instituted and enforced by authorities so that devices and systems capable of detecting leakages of oils and other hazardous liquids must be installed. These liquid leakage detection devices or systems must have a high reliability and must be dependable in operation, so that any leakage may be immediately and accurately detected.
In FIG. 1 a prior art structure is shown which is a liquid leakage detection device of electrical capacitance type. A float 1 is shown floating in a sump or reservoir, or is disposed at a predetermined level in a pit which is emptied. Electrodes 3 are attached to the interior wall surface of the float 1 at a position corresponding to the water line 2 of the float 1, and a weak, high-frequency signal from an electronic circuit 4 is normally applied to the electrodes. When no oil is leaking, the high-frequency current applied to the electrodes 3 is dissipated through the wall, which is fabricated by synthetic resins into the water or a stand (not shown). When the leaking oil flows into the sump, reservoir or pit, the effective dielectric constant of the wall adjacent to the electrodes 3 varies due to the adhesion of the oil 5 to the wall. As a result, the high-frequency current dissipation is reduced and is detected by the electronic circuit 4. In response to the detection signal transmitted through a cable 6 from the electronic circuit 4, an alarm device (not shown) is actuated to give visual and/or sound alarms. The water-line of the float 1 and hence the position of the electrodes 3 may be adjusted by selecting a suitable weight 7 to be placed in float 1.
However, the oil leakage detection device of the type described above cannot detect the leakage of oil until the oil, which has leaked accumulates to relatively great volume. That is, the response is so slow that suitable countermeasures against the oil leakage cannot be taken quickly. Furthermore, the prior art detection device cannot pinpoint a leaking place. Moreover, since the float is placed in the oil, it must be explosion-proof.
Accordingly, one of the objects of the present invention is to provide a liquid leakage detection system which may substantially overcome the above and other problems encountered in the prior art liquid leakage detection devices and a system which is very simple in construction yet highly reliable in operation.
The present invention will become apparent from the following description of some preferred embodiments thereof taken in conjunction with the accompanying drawings.